What causes that? Not mine . It's in a 383 Hammerhead engine? He's been chasing it for awhile now .

If it's running rich, has blow-by, if a carb drips after it has been shut down,.....

A compression/leak down test will rule out the blow-by, but you can also remove one of the oil filler caps and watch for puffs of smoke that coincide with combustion. The dripping is obviously a visual check but the fuel/air mixture could be caused by several things.